1. Field of the Invention
The present invention relates to a light-shielding blade required to effect high-speed movement, such as a shutter blade for use in a focal plane shutter or a lens shutter of a camera, or a diaphragm blade.
2. Related Background Art
Such light-shielding blade is preferably capable of high speed movement with a small driving force and with a sufficiently high bending rigidity, and, for this reason, there is required a light-shielding blade of light weight, high strength and high rigidity. For use in such light-shielding blade, there is already known, as disclosed in the Japanese Laid-open Pat. Sho No. 59-61827 of the present applicant, a plate material composed of plural reinforced plastic sheets which are reinforced with continuous carbon fibers aligned in one direction and which are laminated plane symmetrically in the direction of thickness in such a manner that the directions of said fibers are perpendicular or substantially perpendicular between the neighboring sheets. A light-shielding blade can be obtained by cutting said plate material in a desired shape. However such light-shielding blade has been associated with scattered portions lacking light-shielding ability, such as pinholes, because of the thickness as small as 60 to 120.mu..
For this reason, it has been customary to provide both surfaces of the light-shielding blade with black coatings of a thickness of 5 to 10.mu.. Said black coating can be obtained by applying black paint usually called dry lube, and hardening said paint by drying. In addition to the ensuring of light-shielding property, said black coating also serves for antireflection, improvement of lubrication and appearance.
However, the light-shielding blade having such black coatings has been associated with drawbacks of (1) a high defect rate due to bending of the blade after coating, (2) a high defect rate in terms of precision of thickness, because of significant unevenness in the thickness, and (3) insufficient stability in high-speed motion.